Shruthi New Ppt

8/3/2019 Shruthi New Ppt

1/33

PROTEIN SRUCTURES

BYSHRUTHI REDDY

10011G0620


2/33

Importance of Proteins

Musclestructure depends onprotein-proteininteractions Transportacross membranesinvolvesprotein-solute

interactions

Nerveactivityrequirestransmittersubstance-proteininteractions

Immuneprotectionrequiresantibody-antigeninteractions


3/33

StructuralStructural

MovementMovement

TransportTransport

StorageStorage

HormoneHormone

ProtectionProtection

EnzymesEnzymes

CollagenCollagen; bones, tendons, cartilageKeratinKeratin; hair, skin, wool, nails, feathers

Myosin & ActinMyosin & Actin; muscle contractions

HemoglobinHemoglobin; transports O2LipoproteinsLipoproteins; transports lipids

CaseinCasein; in milk. AlbuminAlbumin; in eggs

InsulinInsulin; regulates blood glucose

Growth hormoneGrowth hormone; regulates growthImmunoglobulinsImmunoglobulins; stimulate immunitySnake venomSnake venom;; plant toxinsplant toxins;

SucraseSucrase; catalyzes sucrose hydrolysisPepsinPepsin; catalyzes protein hydrolysis

Functions of Proteins


4/33

Protein Structure

20 Amino Acids

Primary

Secondary

Tertiary

Quaternary

Denatured

( )

Coded in DNA

Self assembly to a single (native)

structure. Depends on primary

structure and solution conditions

Common in foods. Many non-

native forms depending on

protein structure, solution

conditions (& history) andingredient interactions


5/33

16.2 Amino Acids

Amino acids Arethe building blocks ofproteins. Containacarboxylicacid groupand anamino group

onthealpha (E

) carbon. Areionized insolution. Eachcontaina differentsidegroup (R).

R R +

H2NCCOOH H3NCCOO H H

ionized form


6/33

Amino Acids

The monomerunit ofproteins

C C

H

NH2

R

HO

O

R istheside chain.One of 20 differentchemicalcompounds

Some R-groupsareacid(otheralkali)Some R-groupsarewatersoluble (othersare

not)

Chiral carbon (L-

series)


7/33

Types of Amino Acids

Amino acidsareclassified as

Nonpolar(hydrophobic)withhydrocarbonside

chains. Polar(hydrophilic) with

polarorionicsidechains.

Acidic (hydrophilic) with

acidicsidechains. Basic (hydrophilic) with

NH2 sidechains.

Nonpolar Polar

Acidic Basic

Copyright 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings


8/33

Nonpolar Amino Acids

A nonpolaramino acid has An R groupthatis H, analkylgroup, oraromatic.



9/33

Polar Amino Acids

A polaramino acid has An R groupthatisanalcohol, thiol, oramide.



10/33

Acidic and Basic Amino Acids

Anamino acid is Acidic withacarboxyl R group (COO). Basic withanamino R group (NH3+).

Copyright 2007 by Pearson Education, Inc.

Publishing as Benjamin Cummings

Basic Amino Acids


11/33

Formation of Peptides

Copyright 2007 by Pearson Education, IncPublishing as Benjamin Cummings


12/33

The Peptide Bond

A peptide bond Isanamide bond. Forms betweenthecarboxylgroup of oneamino acid

and theamino group ofthenextamino acid.

O CH3 O+ || + | ||

H3NCH2CO + H3NCHCO

O H CH3 O+ || | | ||

H3NCH2CNCHCO + H2Opeptide bond


13/33

Overview

Primary Structure Secondary Structure Tertiary Structure

Quaternary Structure


14/33

Primary Structure of Proteins

Theprimarystructure ofaproteinis Theparticularsequence ofamino acids. The backbone ofapeptidechain orprotein.

AlaLeuCysMet

CH3

SH

CH2

CH3

S

CH2

CH2

CH O

O-

CCH

H

N

O

CCH

H

N

O

CCH

H

N

O

CCHH3N

CH3

CH3

CH



15/33

Primary Structures

Thenonapeptides oxytocinand vasopressin Havesimilarprimarystructures. Differonlyintheamino acidsatpositions 3 and 8.

Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings


16/33

Primary Structure

of Insu

linInsulin Wasthe firstproteinto

haveitsprimarystructure

determined. Hasaprimarystructure of

two polypeptidechainslinked by disulfide bonds.

Hasachain A with 21amino acidsand achain Bwith 30 amino acids.



17/33

Secondary Structure Alpha Helix

Thesecondarystructures ofproteinsindicatethethree-dimensionalspatialarrangements ofthepolypeptidechains.

An alphahelix has A coiled shapeheld inplace byhydrogen bonds

betweentheamidegroupsand thecarbonyl

groups oftheamino acidsalongthechain. Hydrogen bonds betweenthe H ofa N-H group

and theO ofC=O ofthe fourthamino acid downthechain.


18/33

Secondary Structure Alpha Helix



19/33

Secondary Structure Beta

Pleated SheetA beta-pleated sheetisasecondarystructurethat Consists ofpolypeptidechainsarranged side by

side. Hashydrogen bonds betweenchains. Has R groupsaboveand below thesheet. Istypical of fibrousproteinssuchassilk.


20/33

Secondary Structure: -Pleated

Sheet



21/33

Secondary Structure: Triple Helix

A triplehelix Consists ofthreealpha

helix chains woventogether.

Containslargeamountsglycine, proline, hydroxyproline, andhydroxylysinethatcontain

OH groups forhydrogenbonding.

Is found incollagen,connectivetissue, skin,tendons, and cartilage.



22/33

Thetertiarystructureofaprotein Givesaspecificthree dimensionalshapeto the

polypeptidechain. Involvesinteractionsand crosslinks between

differentparts ofthepeptidechain. Isstabilized by

Hydrophobicand hydrophilicinteractions.

Salt bridges.Hydrogen bonds.Disulfide bonds.

Tertiary Structure


23/33

Tertiary Structure

non-linear

3 dimensional

global but restricted to the

amino acid polymer

formed and stabilized by

hydrogen bonding, covalent(e.g. disulfide) bonding,

hydrophobic packing toward

core and hydrophilic

exposure to solvent

A globular amino acidpolymer folded and

compacted is somewhat

functional (catalytic) and

energetically favorable

interaction!


24/33

Tertiary Structure

Theinteractionsofthe R groupsgiveaproteinits specificthree-

dimensionaltertiarystructure.



25/33

Globular Proteins

Globularproteins Havecompact,

sphericalshapes.

Carry outsynthesis,transport, andmetabolism inthecells.

Suchas myoglobinstoreand transportoxygenin muscle.

Myoglobin



26/33

Fibrous Proteins

Fibrousproteins Consist oflong, fiber-likeshapes. Suchasalphakeratins makeuphair, wool, skin,

and nails. Suchas featherscontain betakeratins withlargeamounts of beta-pleated sheetstructures.



27/33


non-linear 3 dimensional

global, and across

distinct amino acid

polymers

formed by hydrogen

bonding, covalent

bonding, hydrophobic

packing and hydrophilic

exposure favorable, functional

structures occur

frequently and have been

categorized


28/33


The quaternarystructure Isthecombination oftwo or

moretertiaryunits.

Issta

bilize

d bythe

sa

meinteractions found intertiary

structures.

Ofhemoglobinconsists oftwoalphachainsand two beta

chains. Thehemegroupineachsubunitpicksup oxygenfortransportinthe blood to thetissues.


hemoglobin


29/33

Protein Structure Determination

High-resolutionstructure determination X-raycrystallography (~1) Nuclearmagneticresonance (NMR) (~1-2.5)

Low-resolutionstructure determination Cryo-EM (electron-microscropy) ~10-15


30/33

X-ray crystallography

mostaccurate Anextremelypureproteinsampleisneeded.

Theproteinsample must form crystalsthatarerelativelylarge

with

out

fla

ws.

Generally the biggest problem.

Manyproteinsarentamenableto crystallizationatall(i.e., proteinsthat do theirworkinside ofacellmembrane).

~$100K perstructure


31/33

NuclearMagnetic Resonance

Fairlyaccurate

No need forcrystals

limited to small, solubleproteins only.


32/33

Protein: TheMachinery of Life

Lifeisthe mode ofexistence ofproteins, and thismode ofexistenceessentiallyconsistsintheconstantself-renewal ofthechemicalconstituentsofthesesubstances.

Friedrich Engles, 1878

NH2-Val-His-Leu-Thr-Pro-Glu-Glu-Lys-Ser-Ala-Val-Thr-Ala-Leu-Trp-Gly-Lys-Val-Asn-Val-Asp-Glu-Val-Gly-Gly-Glu-..


33/33

THANK YOU

Shruthi New Ppt

Documents

Transcript of Shruthi New Ppt